But while Cialdini may be the field’s best known name, a new wave of researchers is following in his footsteps, continuing to investigate what really works when it comes to influencing others, and what advice amounts to old wives’ tales.

Some of what they’ve uncovered seems counter-intuitive. Other ideas appear too simple to possible be effective. “The idea that adding only a few words to a request can have dramatic increases in compliance sounds like Ali Baba saying ‘open sesame’ to reveal a secret cave,” one of this next wave of persuasion researchers, Christopher Carpenter, a professor of communication at Western Illinois University, told Yesware, for example. Carpenter’s work has helped to uncover the fact that simply telling your prospect that he or she is free to say no doubles the chance of getting them to say yes. That may seem impossible, but science says it’s true.

So what other simple and practical persuasion principles have researchers recently turned up that even devoted fans of standard persuasion science may not yet have heard of? Here are three:

The Eyes are the Window of the Soul?

Perhaps you’ve heard the conventional wisdom about the persuasive power of looking someone in the eye. University of British Columbia psychology professor Frances Chen heard it too. “There is a lot of cultural lore about the power of eye contact as an influence — for example, the expression that ‘the eyes are the windows to the soul,’ or the demands that people sometimes make in the middle of an argument: ‘Look at me when I am talking to you!’” she says.

But is this standard wisdom of grandfathers actually accurate? Chen and her colleagues decided to test whether more eye contact really made you more persuasive. Turns out, it’s subtler than dozens of business gurus and classic movie heroes would have you believe. When Chen’s team used eye-tracking technology to look at how listeners reacted to extended eye contact they discovered more really wasn’t always better.

The takeaway for sales pros is simple. “My advice to a speaker who wants to use eye contact in a persuasion attempt is to pay attention to the body language of the listener. If the listener seems receptive and open to your message, direct eye contact can (as popular belief suggests) have a positive impact on persuasion. However, if he or she seems upset, overwhelmed, or starts looking away, trying to force direct eye contact might backfire,” Chen explains. So don’t take your straight-talking sheriff routine too far.

Whatever you’re trying to sell, you might suspect that the more reasons you can give the listener to buy in the better you’ll do. But research from Kurt Carlson, a professor of Marketing at Georgetown, and others found otherwise. “Pretty much all of the previous research found that four was better than three and five was better than four, etc,” Carlson told Yesware, “but this work was done in basic psychology years ago, and we found that it didn’t examine situations where the person reacting to the claims was aware the person making the claims might have a persuasion motive.”

What happens when your prospect is on to the fact that you might be trying to sell them something? If you give them too many reasons, like Hamlet’s mother, they start to suspect that the lady doth protest too much. “When someone goes beyond three, they appear to be providing more information than is necessary to get the job done. When a consumer is aware that the person crafting the message might want to persuade them, they see this information overreach as a persuasion attempt. Essentially the fourth claim causes them to become skeptical,” Carlson says.

Come On, Make Up Your Mind!

Or maybe don’t.

Stanford’s Zackary Tormala has devoted much of his career to studying how to get people to change their minds, including reinforcing the previously well known piece of persuasion wisdom that says some folks are more likely to be convinced by rational arguments while others prefer emotion-based ones. His work added to this classic bit of influence wisdom by showing that something as simple as swapping the verb ‘think’ for ‘feel’ to match a listener’s cognitive preference (and making no other change to the message) could impact how persuasive the listener found the argument.

“If you speak the same language as your audience, you’ll generally be more persuasive,” Tormala explained. But that, he said, wasn’t the most counterintuitive finding his research has turned up. While many salespeople naturally strive to squash prospects’ doubts, Tormala’s findings suggest that many persuasion professionals fail to fully appreciate the value of uncertainty.

“One principle that I believe should be better known is that uncertainty can be a powerful persuasion lever. In lots of different studies, we have found that uncertainty can motivate people to think more deeply or process more carefully,” he says.

How does that work in practice? “For instance, in one set of studies we found that experts could get people to think more about their message, which gave it more impact, when they expressed some level of uncertainty about what they were saying,” he elaborates.

So why might be good to get those you’re trying to truly bring around to your way of thinking to acknowledge and express their doubt? “We found that this occurs because the uncertainty surrounding potential gets people thinking more, and as long as what they’re thinking about is positive or compelling in some way, thinking more about it can promote more persuasion,” Tormala explains.